1. Field of the Invention
This invention relates to a dew condensation preventing structure, and more particularly to a dew condensation preventing structure forming a space and a dew condensation preventing steel door disposed at the entrance to a room.
2. Prior Art
In a room of a highly air-tight condominium or hotel for example, using a heater increases humidity and may result in giving a person an unpleasant feeling.
To provide a comfortable room for people, there have been developed wall, ceiling and other dew condensation preventing structures which prevent the occurrence of dew condensation by suitably adjusting moisture in a room.
FIG. 6 shows a dew condensation preventing structure for forming such a room, in which reference numeral 11 denotes a dew condensation preventing structure consisting of walls for forming a space 13.
This dew condensation preventing structure 11 consists of a concrete base 15. On the surface of this concrete base 15 on the space 13 side, a heat-insulating layer 17 is formed. And on the surface of the heat-insulating layer 17 on the space 13 side, a plaster board 19 having fire retardance is bonded by bonding agent 18.
The surface of this plaster board 19 on the space 13 side has a moisture absorbing and releasing layer 21 formed which absorbs moisture when the humidity in the space 13 is high and naturally releases moisture when the humidity is low. This moisture absorbing and releasing layer 21 is formed by having for example a wall paper bonded which can holds 200 to 300 g/m.sup.2 of moisture. And, to give a moisture absorbing and releasing property to the wall paper of the moisture absorbing and releasing layer 21, it is formed in combination with material having a moisture absorbing and releasing property, such as a high water-absorbing polymer for example.
And the heat-insulating layer 17 is made of an organic heat insulator such as expanded urethane or Styrofoam (registered trademark).
In the above dew condensation preventing structure forming a space as described above, the heat-insulating layer 17 excludes the outside heat from entering and the moisture absorbing and releasing layer 21 adjusts the moisture in the space 13 to keep the humidity in the space 13 at a level that people feel comfortable and to suppress the occurrence of dew condensation.
But, the organic heat insulator such as expanded urethane and Styrofoam forming the heat-insulating layer 17 has such a low thermal conductivity of 0.02 to 0.03 (kcal/mhr.sup..degree. C.) that it has remarkable heat-insulating performance but has a disadvantage that it is easily flammable because it is organic.
In view of legal fire preventing regulations and strength, it is necessary to bond a flame retardant plaster board 19 to the surface of heat-insulating layer 17 on the space 13 side to form a base on which the moisture absorbing and releasing layer 21 consisting of a wall paper is applied. This results in disadvantages requiring many construction steps, much labor and making the space 13 narrow.
To solve the above disadvantages, the heat-insulating layer 17 is proposed to be made of an inorganic heat insulator such as expanded mortar or pearlite mortar.
The above inorganic heat insulator is not easily flammable. But it has a thermal conductivity of 0.2 to 0.3 (kcal/mhr.sup..degree. C.) which is exceptionally larger than that (0.02 to 0.03 kcal/mhr.sup..degree. C.) of an organic heat insulator. Thus, it has a disadvantage that its heat-insulating performance is inferior to that of the organic heat insulator.
Therefore, it is difficult to obtain a desired heat insulating performance. And to obtain the desired performance, a very thick material is required.
When the heat-insulating performance could be improved for the above inorganic heat insulator, its strength was adversely deteriorated. Therefore, it had a problem that it did not function as a base on which finishing was applied.
On the other hand, each apartment of an apartment house has a manufactured steel entrance door in view of fire preventing regulations.
These years, at the so-called "water-using area" near the entrance, a bathroom unit including a basin, a bathtub and a toilet is often disposed. Humidity at the corridor from the bathroom to the entrance or the space connecting the entrance and the bathroom is high. From autumn to winter, when the temperature falls, air with a high humidity touches to the surface of the steel front entrance door on the room side, and moisture in the air reached a dew point concentrates on the steel door surface. Very small waterdrops formed on the door grow larger and fall down to deeply wet the lower section of the door, outside floor, and the inside corridor.
To prevent the occurrence of dew condensation on the steel door, it is proposed to lower the humidity of the air in the corridor or connecting space, or to warm the steel door surface to over the dew point.
However, when anyone enters or leaves the bathroom, moisture-containing air flows into the corridor or connecting space, raising the humidity. Thus, it is very difficult to lower the humidity in the corridor or connecting space.
And, there is an idea of warming the steel door surface to above the dew point by employing a method used for heating an automobile window glass by arranging an electrical resistance to flow a current through it. But this is also very difficult because the steel door is not a nonconductor unlike the window glass.